An example of a composite gear wherein an internal gear is formed on the inner peripheral surface thereof and an external gear (convex portion) is formed on the outer peripheral surface thereof is disclosed in Japanese Utility Model Laid-Open Publication No. Sho 63-87344. The composite gear disclosed in Japanese Utility Model Laid-Open Publication No. Sho 63-87344 is used as a ring gear of a planetary gear reduction unit in an engine starting device equipped with the planetary gear reduction unit between a drive shaft and an output rotating shaft. With this type of a composite gear, a rotation support surface which is a surface rotatably supported by a bearing is usually provided on the external peripheral surface thereof.
Also, as another background art, a gear loading device for setting gears on gear processing machines is disclosed in Japanese Patent Laid-Open Publication No. Hei 6-114672.
With a composite gear where an external gear is formed on the outer peripheral surface thereof and an internal gear is formed on the inner peripheral surface thereof, machining of the external gear is implemented with the outside being chucked at the rotation support surface of the outside peripheral surface. However, since the rotation support surface is a surface rotatably supported by a bearing, the rotation support surface needs to be subjected to finishing machining after the external gear is machined. As a result, in the case where the external gears is machined with the outside being chucked at the rotation support surface of the outside peripheral surface, the datum for locating a workpiece during machining of the external gear and that used during machining of the rotation support surface differ. Accordingly, there is a problem that the precision of the external gear is degraded.
The purpose of the present invention is to provide a composite gear and method of manufacturing the same that can improve the precision of the external gear.